src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2010 Guus Sliepen <guus@tinc-vpn.org>
   5                   2010      Timothy Redaelli <timothy@redaelli.eu>
   6
   7     This program is free software; you can redistribute it and/or modify
   8     it under the terms of the GNU General Public License as published by
   9     the Free Software Foundation; either version 2 of the License, or
  10     (at your option) any later version.
  11
  12     This program is distributed in the hope that it will be useful,
  13     but WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15     GNU General Public License for more details.
  16
  17     You should have received a copy of the GNU General Public License along
  18     with this program; if not, write to the Free Software Foundation, Inc.,
  19     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20 */
  21
  22 #include "system.h"
  23
  24 #include <openssl/rand.h>
  25 #include <openssl/err.h>
  26 #include <openssl/evp.h>
  27 #include <openssl/pem.h>
  28 #include <openssl/hmac.h>
  29
  30 #ifdef HAVE_ZLIB
  31 #include <zlib.h>
  32 #endif
  33
  34 #ifdef HAVE_LZO
  35 #include LZO1X_H
  36 #endif
  37
  38 #include "splay_tree.h"
  39 #include "cipher.h"
  40 #include "conf.h"
  41 #include "connection.h"
  42 #include "crypto.h"
  43 #include "digest.h"
  44 #include "device.h"
  45 #include "ethernet.h"
  46 #include "graph.h"
  47 #include "list.h"
  48 #include "logger.h"
  49 #include "net.h"
  50 #include "netutl.h"
  51 #include "protocol.h"
  52 #include "process.h"
  53 #include "route.h"
  54 #include "utils.h"
  55 #include "xalloc.h"
  56
  57 int keylifetime = 0;
  58 int keyexpires = 0;
  59 #ifdef HAVE_LZO
  60 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  61 #endif
  62
  63 static void send_udppacket(node_t *, vpn_packet_t *);
  64
  65 #define MAX_SEQNO 1073741824
  66
  67 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  68 // mtuprobes ==    31: sleep pinginterval seconds
  69 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  70 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  71
  72 static void send_mtu_probe_handler(int fd, short events, void *data) {
  73         node_t *n = data;
  74         vpn_packet_t packet;
  75         int len, i;
  76         int timeout = 1;
  77
  78         n->mtuprobes++;
  79
  80         if(!n->status.reachable || !n->status.validkey) {
  81                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  82                 n->mtuprobes = 0;
  83                 return;
  84         }
  85
  86         if(n->mtuprobes > 32) {
  87                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  88                 n->mtuprobes = 1;
  89                 n->minmtu = 0;
  90                 n->maxmtu = MTU;
  91         }
  92
  93         if(n->mtuprobes >= 10 && !n->minmtu) {
  94                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  95                 n->mtuprobes = 0;
  96                 return;
  97         }
  98
  99         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
 100                 if(n->minmtu > n->maxmtu)
 101                         n->minmtu = n->maxmtu;
 102                 else
 103                         n->maxmtu = n->minmtu;
 104                 n->mtu = n->minmtu;
 105                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
 106                 n->mtuprobes = 31;
 107         }
 108
 109         if(n->mtuprobes == 31) {
 110                 timeout = pinginterval;
 111                 goto end;
 112         } else if(n->mtuprobes == 32) {
 113                 timeout = pingtimeout;
 114         }
 115
 116         for(i = 0; i < 3; i++) {
 117                 if(n->maxmtu <= n->minmtu)
 118                         len = n->maxmtu;
 119                 else
 120                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 121
 122                 if(len < 64)
 123                         len = 64;
 124
 125                 memset(packet.data, 0, 14);
 126                 randomize(packet.data + 14, len - 14);
 127                 packet.len = len;
 128                 packet.priority = 0;
 129
 130                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 131
 132                 send_udppacket(n, &packet);
 133         }
 134
 135 end:
 136         event_add(&n->mtuevent, &(struct timeval){timeout, 0});
 137 }
 138
 139 void send_mtu_probe(node_t *n) {
 140         if(!timeout_initialized(&n->mtuevent))
 141                 timeout_set(&n->mtuevent, send_mtu_probe_handler, n);
 142         send_mtu_probe_handler(0, 0, n);
 143 }
 144
 145 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 146         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 147
 148         if(!packet->data[0]) {
 149                 packet->data[0] = 1;
 150                 send_udppacket(n, packet);
 151         } else {
 152                 if(len > n->maxmtu)
 153                         len = n->maxmtu;
 154                 if(n->minmtu < len)
 155                         n->minmtu = len;
 156                 if(n->mtuprobes > 30)
 157                         n->mtuprobes = 30;
 158         }
 159 }
 160
 161 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 162         if(level == 0) {
 163                 memcpy(dest, source, len);
 164                 return len;
 165         } else if(level == 10) {
 166 #ifdef HAVE_LZO
 167                 lzo_uint lzolen = MAXSIZE;
 168                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 169                 return lzolen;
 170 #else
 171                 return -1;
 172 #endif
 173         } else if(level < 10) {
 174 #ifdef HAVE_ZLIB
 175                 unsigned long destlen = MAXSIZE;
 176                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 177                         return destlen;
 178                 else
 179 #endif
 180                         return -1;
 181         } else {
 182 #ifdef HAVE_LZO
 183                 lzo_uint lzolen = MAXSIZE;
 184                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 185                 return lzolen;
 186 #else
 187                 return -1;
 188 #endif
 189         }
 190
 191         return -1;
 192 }
 193
 194 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 195         if(level == 0) {
 196                 memcpy(dest, source, len);
 197                 return len;
 198         } else if(level > 9) {
 199 #ifdef HAVE_LZO
 200                 lzo_uint lzolen = MAXSIZE;
 201                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 202                         return lzolen;
 203                 else
 204 #endif
 205                         return -1;
 206         }
 207 #ifdef HAVE_ZLIB
 208         else {
 209                 unsigned long destlen = MAXSIZE;
 210                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 211                         return destlen;
 212                 else
 213                         return -1;
 214         }
 215 #endif
 216
 217         return -1;
 218 }
 219
 220 /* VPN packet I/O */
 221
 222 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 223         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 224                            packet->len, n->name, n->hostname);
 225
 226         route(n, packet);
 227 }
 228
 229 static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
 230         if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
 231                 return false;
 232
 233         return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
 234 }
 235
 236 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 237         vpn_packet_t pkt1, pkt2;
 238         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 239         int nextpkt = 0;
 240         vpn_packet_t *outpkt = pkt[0];
 241         size_t outlen;
 242         int i;
 243
 244         if(!cipher_active(&n->incipher)) {
 245                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 246                                         n->name, n->hostname);
 247                 return;
 248         }
 249
 250         /* Check packet length */
 251
 252         if(inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest)) {
 253                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 254                                         n->name, n->hostname);
 255                 return;
 256         }
 257
 258         /* Check the message authentication code */
 259
 260         if(digest_active(&n->indigest)) {
 261                 inpkt->len -= n->indigest.maclength;
 262                 if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
 263                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
 264                         return;
 265                 }
 266         }
 267         /* Decrypt the packet */
 268
 269         if(cipher_active(&n->incipher)) {
 270                 outpkt = pkt[nextpkt++];
 271                 outlen = MAXSIZE;
 272
 273                 if(!cipher_decrypt(&n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 274                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
 275                         return;
 276                 }
 277
 278                 outpkt->len = outlen;
 279                 inpkt = outpkt;
 280         }
 281
 282         /* Check the sequence number */
 283
 284         inpkt->len -= sizeof inpkt->seqno;
 285         inpkt->seqno = ntohl(inpkt->seqno);
 286
 287         if(inpkt->seqno != n->received_seqno + 1) {
 288                 if(inpkt->seqno >= n->received_seqno + sizeof n->late * 8) {
 289                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 290                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 291
 292                         memset(n->late, 0, sizeof n->late);
 293                 } else if (inpkt->seqno <= n->received_seqno) {
 294                         if((n->received_seqno >= sizeof n->late * 8 && inpkt->seqno <= n->received_seqno - sizeof n->late * 8) || !(n->late[(inpkt->seqno / 8) % sizeof n->late] & (1 << inpkt->seqno % 8))) {
 295                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 296                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 297                                 return;
 298                         }
 299                 } else {
 300                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 301                                 n->late[(i / 8) % sizeof n->late] |= 1 << i % 8;
 302                 }
 303         }
 304
 305         n->late[(inpkt->seqno / 8) % sizeof n->late] &= ~(1 << inpkt->seqno % 8);
 306
 307         if(inpkt->seqno > n->received_seqno)
 308                 n->received_seqno = inpkt->seqno;
 309
 310         if(n->received_seqno > MAX_SEQNO)
 311                 regenerate_key();
 312
 313         /* Decompress the packet */
 314
 315         length_t origlen = inpkt->len;
 316
 317         if(n->incompression) {
 318                 outpkt = pkt[nextpkt++];
 319
 320                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 321                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 322                                                  n->name, n->hostname);
 323                         return;
 324                 }
 325
 326                 inpkt = outpkt;
 327
 328                 origlen -= MTU/64 + 20;
 329         }
 330
 331         inpkt->priority = 0;
 332
 333         if(!inpkt->data[12] && !inpkt->data[13])
 334                 mtu_probe_h(n, inpkt, origlen);
 335         else
 336                 receive_packet(n, inpkt);
 337 }
 338
 339 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 340         vpn_packet_t outpkt;
 341
 342         outpkt.len = len;
 343         if(c->options & OPTION_TCPONLY)
 344                 outpkt.priority = 0;
 345         else
 346                 outpkt.priority = -1;
 347         memcpy(outpkt.data, buffer, len);
 348
 349         receive_packet(c->node, &outpkt);
 350 }
 351
 352 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 353         vpn_packet_t pkt1, pkt2;
 354         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 355         vpn_packet_t *inpkt = origpkt;
 356         int nextpkt = 0;
 357         vpn_packet_t *outpkt;
 358         int origlen;
 359         size_t outlen;
 360 #if defined(SOL_IP) && defined(IP_TOS)
 361         static int priority = 0;
 362 #endif
 363         int origpriority;
 364         int sock;
 365
 366         if(!n->status.reachable) {
 367                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 368                 return;
 369         }
 370
 371         /* Make sure we have a valid key */
 372
 373         if(!n->status.validkey) {
 374                 time_t now = time(NULL);
 375
 376                 ifdebug(TRAFFIC) logger(LOG_INFO,
 377                                    "No valid key known yet for %s (%s), forwarding via TCP",
 378                                    n->name, n->hostname);
 379
 380                 if(n->last_req_key + 10 < now) {
 381                         send_req_key(n);
 382                         n->last_req_key = now;
 383                 }
 384
 385                 send_tcppacket(n->nexthop->connection, origpkt);
 386
 387                 return;
 388         }
 389
 390         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 391                 ifdebug(TRAFFIC) logger(LOG_INFO,
 392                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 393                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 394
 395                 if(n != n->nexthop)
 396                         send_packet(n->nexthop, origpkt);
 397                 else
 398                         send_tcppacket(n->nexthop->connection, origpkt);
 399
 400                 return;
 401         }
 402
 403         origlen = inpkt->len;
 404         origpriority = inpkt->priority;
 405
 406         /* Compress the packet */
 407
 408         if(n->outcompression) {
 409                 outpkt = pkt[nextpkt++];
 410
 411                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 412                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 413                                    n->name, n->hostname);
 414                         return;
 415                 }
 416
 417                 inpkt = outpkt;
 418         }
 419
 420         /* Add sequence number */
 421
 422         inpkt->seqno = htonl(++(n->sent_seqno));
 423         inpkt->len += sizeof inpkt->seqno;
 424
 425         /* Encrypt the packet */
 426
 427         if(cipher_active(&n->outcipher)) {
 428                 outpkt = pkt[nextpkt++];
 429                 outlen = MAXSIZE;
 430
 431                 if(!cipher_encrypt(&n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 432                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
 433                         goto end;
 434                 }
 435
 436                 outpkt->len = outlen;
 437                 inpkt = outpkt;
 438         }
 439
 440         /* Add the message authentication code */
 441
 442         if(digest_active(&n->outdigest)) {
 443                 digest_create(&n->outdigest, &inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len);
 444                 inpkt->len += digest_length(&n->outdigest);
 445         }
 446
 447         /* Determine which socket we have to use */
 448
 449         for(sock = 0; sock < listen_sockets; sock++)
 450                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 451                         break;
 452
 453         if(sock >= listen_sockets)
 454                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 455
 456         /* Send the packet */
 457
 458 #if defined(SOL_IP) && defined(IP_TOS)
 459         if(priorityinheritance && origpriority != priority
 460            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 461                 priority = origpriority;
 462                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 463                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof priority))     /* SO_PRIORITY doesn't seem to work */
 464                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 465         }
 466 #endif
 467
 468         if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) {
 469                 if(sockmsgsize(sockerrno)) {
 470                         if(n->maxmtu >= origlen)
 471                                 n->maxmtu = origlen - 1;
 472                         if(n->mtu >= origlen)
 473                                 n->mtu = origlen - 1;
 474                 } else
 475                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 476         }
 477
 478 end:
 479         origpkt->len = origlen;
 480 }
 481
 482 /*
 483   send a packet to the given vpn ip.
 484 */
 485 void send_packet(const node_t *n, vpn_packet_t *packet) {
 486         node_t *via;
 487
 488         if(n == myself) {
 489                 if(overwrite_mac)
 490                          memcpy(packet->data, mymac.x, ETH_ALEN);
 491                 write_packet(packet);
 492                 return;
 493         }
 494
 495         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 496                            packet->len, n->name, n->hostname);
 497
 498         if(!n->status.reachable) {
 499                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 500                                    n->name, n->hostname);
 501                 return;
 502         }
 503
 504         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 505
 506         if(via != n)
 507                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 508                            n->name, via->name, n->via->hostname);
 509
 510         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 511                 if(!send_tcppacket(via->connection, packet))
 512                         terminate_connection(via->connection, true);
 513         } else
 514                 send_udppacket(via, packet);
 515 }
 516
 517 /* Broadcast a packet using the minimum spanning tree */
 518
 519 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 520         splay_node_t *node;
 521         connection_t *c;
 522
 523         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 524                            packet->len, from->name, from->hostname);
 525
 526         if(from != myself) {
 527                 send_packet(myself, packet);
 528
 529                 // In TunnelServer mode, do not forward broadcast packets.
 530                 // The MST might not be valid and create loops.
 531                 if(tunnelserver)
 532                         return;
 533         }
 534
 535         for(node = connection_tree->head; node; node = node->next) {
 536                 c = node->data;
 537
 538                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 539                         send_packet(c->node, packet);
 540         }
 541 }
 542
 543 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 544         splay_node_t *node;
 545         node_t *n, *found = NULL;
 546         static time_t last_hard_try = 0;
 547         time_t now = time(NULL);
 548
 549         if(last_hard_try == now)
 550                 return NULL;
 551         else
 552                 last_hard_try = now;
 553
 554         for(node = node_tree->head; node; node = node->next) {
 555                 n = node->data;
 556
 557                 if(n == myself || !n->status.reachable || !digest_active(&n->indigest))
 558                         continue;
 559
 560                 if(try_mac(n, pkt)) {
 561                         found = n;
 562                         break;
 563                 }
 564         }
 565
 566         return found;
 567 }
 568
 569 void handle_incoming_vpn_data(int sock, short events, void *data) {
 570         vpn_packet_t pkt;
 571         char *hostname;
 572         sockaddr_t from;
 573         socklen_t fromlen = sizeof from;
 574         node_t *n;
 575         int len;
 576
 577         len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 578
 579         if(len <= 0 || len > MAXSIZE) {
 580                 if(!sockwouldblock(sockerrno))
 581                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 582                 return;
 583         }
 584
 585         pkt.len = len;
 586
 587         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 588
 589         n = lookup_node_udp(&from);
 590
 591         if(!n) {
 592                 n = try_harder(&from, &pkt);
 593                 if(n)
 594                         update_node_udp(n, &from);
 595                 else ifdebug(PROTOCOL) {
 596                         hostname = sockaddr2hostname(&from);
 597                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 598                         free(hostname);
 599                         return;
 600                 }
 601                 else
 602                         return;
 603         }
 604
 605         receive_udppacket(n, &pkt);
 606 }
 607
 608 void handle_device_data(int sock, short events, void *data) {
 609         vpn_packet_t packet;
 610
 611         if(read_packet(&packet))
 612                 route(myself, &packet);
 613 }